Positively associated —larger values of one variable are associated with larger values of the other; see
association
Power of the test —probability of rejecting a null hypothesis against a specific alternative
Probability distribution —identification of the outcomes of a random variable together with the
probabilities associated with those outcomes
Probability histogram —histogram for a probability distribution; horizontal axis shows the outcomes,
vertical axis shows the probabilities of those outcomes
Probability of an event —relative frequency of the number of ways an event can succeed to the total
number of ways it can succeed or fail
Probability sample —sampling technique that uses a random mechanism to select the members of the
sample
Proportion —ratio of the count of a particular outcome to the total number of outcomes
Qualitative data —data whose values range over categories rather than values
Quantitative data —data whose values are numerical
Quartiles —25th, 50th, and 75th percentiles of a dataset
Random phenomenon —unclear how any one trial will turn out, but there is a regular distribution of
outcomes in a large number of trials
Random sample —sample in which each member of the sample is chosen by chance and each member of
the population has an equal chance to be in the sample
Random variable —numerical outcome of a random phenomenon (random experiment)
Randomization —random assignment of experimental units to treatments
Range —difference between the maximum and minimum values of a dataset
Replication —repetition of each treatment enough times to help control for chance variation
Representative sample —sample that possesses the essential characteristics of the population from
which it was taken
Residual —in a regression, the actual value minus the predicted value
Resistant statistic —one whose numerical value is not influenced by extreme values in the dataset
Response bias —bias that stems from respondents’ inaccurate or untruthful response
Response variable —measures the outcome of a study
Robust —when a procedure may still be useful even if the conditions needed to justify it are not
completely satisfied
Robust procedure —procedure that still works reasonably well even if the assumptions needed for it are
violated; the t -procedures are robust against the assumption of normality as long as there are no
outliers or severe skewness.
Sample space —set of all possible mutually exclusive outcomes of a probability experiment
Sample survey —using a sample from a population to obtain responses to questions from individuals
Sampling distribution of a statistic —distribution of all possible values of a statistic for samples of a
given size
Sampling frame —list of experimental units from which the sample is selected
Scatterplot —graphical representation of a set of ordered pairs; horizontal axis is first element in the